Autofill sample: Scaffolding for setting to add mock data.

* This makes it easier to test how your app responds to autofill data.
* Creates a dataset containing data for every View and W3C autofill hint.
* Refactored since there are 60+ hints and references to them were
* getting repetitive. Now all hint metadata is centralized.
* TODO: generate random autofill data for all hints.

Bug: 38182790
Test: manual
Change-Id: Ic525395a6270ba68ca1702aa5c60226037d6c0fb